When it comes to space-strategy games that span an entire galaxy, the two best games out there are Stellaris and Endless Space 2. Both games have players take the role of a space empire as they colonize new planets to take over the galaxy. Both games also have some pretty in-depth mechanics that are pretty typical for 4X grand strategy games that make both Stellaris and Endless Space 2 tricky games to learn.
While both games are a ton of fun once players get past the learning curve, they are both pretty pricy and take a ton of time to learn. Given both the time and monetary investment both games require, it may be better for those looking for their space strategy fix to pick the best of these two games. Each game also appeals to their own sub-groups of sci-fi strategy fans with some unique things each game does when compared to each other.
Stellaris
Given that Stellaris was made by Paradox Interactive, it should be expected that the game will bring a great 4X strategy experience. That being said, those looking to play should also expect to pay a fairly hefty amount for the game and the numerous DLCs. Fans consider most of these DLCs to be borderline required to enjoy Stellaris at its best, though there are a few notable exceptions.
That being said, Stellaris actually has a lot more content than it may initially seem in just the base game. Stellaris differs from most 4X strategy games as there aren't any core playable races. Instead, players can make their own race through the game's in-depth creation tools, allowing full customization of a race's ideologies, government and even what they look like. Players can make custom races for not only themselves but also assign those custom races to CPU players.
In Stellaris, players take on the role of a civilization in a vast universe that has just discovered faster-than-light travel. As such, multiple civilizations are attempting to claim their place across the universe and establish their galactic presence. Given the vast difference in ethics and government these civilizations have, players should expect conflict to arise as they discover the many races that inhabit the galaxy.
This leads to the game being more about diplomacy and politics, though there are plenty of ways for conflicts to turn into a full-fledged war. There are also many technologies that players can research, though the tech tree in Stellaris isn't as complicated as in other 4X strategy games. Many of these technologies help players manage colonies on different planets and produce new resources, many of which will help advance their empire.
There's a lot to do in Stellaris and even more ways to play the game. The customizable races lead to many different playstyles as a civilization can be focused on everything from mass-colonization to environmental preservation. Something that makes these ethics even more unique is that there are polar opposite extremes to each one. While one civilization may be focused on environmental preservation, another could be focused on environmental destruction.
With so much to do in Stellaris, it's reasonable to believe that there may be a lot of balancing issues with the game. While the devs are dedicated to releasing frequent patches that rebalance mechanics and even add new ones, this does mean that relearning the game is often a necessity. Stellaris is not only an expensive game with hit-or-miss DLC; it's also one that requires frequent time to learn as new patches constantly rework the entire experience.
Endless Space 2
Paradox Interactive tends to have a monopoly on popular 4X strategy games, so it's a welcome surprise when a release from another dev gets popular. Endless Space 2, developed by Amplitude Studios, is a lot like Stellaris in that players are a grand sci-fi empire aiming to take over the galaxy and be the last civilization left standing.
The twelve races tend to be the most common choices for players; Endless Space 2 does feature a custom faction option, though it isn't as central to the game as Stellaris's tends to be. Instead, the default races each exemplify the core mechanics in Endless Space 2. There's pretty much a default faction for every kind of playstyle in the game, and there are many different ways people can play Endless Space 2.
Stellaris certainly has a tighter focus on diplomacy, but Endless Space 2 balances things out a bit more. The absolutely massive research tree helps players specialize their empires to the exact kind of playstyle they want, though it does mean that research can feel a bit more overwhelming. Certain factions are also tailored to specific playstyles, meaning knowing what the different factions can do is key to learning the game.
The goal of Endless Space 2 is to expand throughout the universe and colonize planets, competing against the other factions. Outside of that, Endless Space 2 is fairly open-ended and is more focused on players advancing their own factions. Between designing ships, passing laws and exploring the anomalies left behind by long-defeated civilizations, there is a ton of content to explore in Endless Space 2.
Which is Better?
Stellaris and Endless Space 2 have a lot of similarities. They both have gameplay focused on exploring the universe and colonizing galaxies, and they both support tons of different playstyles. Stellaris is a bit more open-ended, though Endless Space 2 is a bit easier to understand. While Stellaris has many different in-game systems dedicated to different mechanics, Endless Space 2 chooses to focus a lot of that complexity on the research system.
As for which game is better, Endless Space 2 is the game that initially comes to mind. While Stellaris is certainly more open-ended and has the more well-made DLC, Endless Space 2 balances complexity with its learning curve far better. With Endless Space 2, players can have more confidence knowing that their playstyle won't be destroyed by a patch, even if some of the game's DLC is borderline unplayable.